Zero Hall conductivity and its electronic origin in a Cr-doped topological insulator

Abstract

We investigate the electronic origin of zero Hall conductivity or the axion insulator phase of a Cr-doped Sb2Te3 film by analyzing the evolution of its band structure upon a magnetic field sweep. By applying a small electric field or using asymmetric doping, we differentiate the coercivities of the two surfaces, so they can form either ferromagnetic (FM) or antiferromagnetic (AFM) alignments. Through the surface-resolved Berry curvature calculations, we demonstrate that the system manifests robust zero Hall plateaus when the two surfaces remain topologically nontrivial and enter a magnetic state which has intrasurface FM and intersurface AFM orderings. Our results provide insights for the understanding of the uncharted issues of axion insulators, complementary to the exciting experimental progress in this realm.